Instruments and methods for stabilization of bony structures

ABSTRACT

The present invention relates to a brace installation instrument placement that is mounted to anchors secured in an animal subject. The installation instrument includes anchor extensions coupled to the anchors. The instrument is movable with respect to the anchors to position a brace in a position more proximate the anchors. The brace can be indexed for insertion at a predetermined orientation with respect to the installation instrument. Methods and techniques for using the installation instrument are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and is a continuation of U.S.patent application Ser. No. 14/525,832, filed on Oct. 28, 2014, which isa continuation of U.S. patent application Ser. No. 13/673,566, filed onNov. 9, 2012, now U.S. Pat. No. 8,900,275, which is a continuation ofU.S. patent application Ser. No. 11/338,412, filed on Jan. 24, 2006, nowU.S. Pat. No. 8,361,124, which is a continuation of U.S. patentapplication Ser. No. 10/443,368, filed on May 22, 2003, now U.S. Pat.No. 7,011,660, which is a continuation application of U.S. patentapplication Ser. No. 10/263,522, filed on Oct. 3, 2002, now U.S. Pat.No. 7,008,422, which is a divisional application of U.S. patentapplication Ser. No. 09/616,581, filed on Jul. 14, 2000, now U.S. Pat.No. 6,530,929, which claims the benefit of the filing dates ofProvisional Application Ser. No. 60/186,729, filed on Mar. 3, 2000 andProvisional Application Ser. No. 60/160,489, filed on Oct. 20, 1999. Thereferenced applications are each incorporated herein by reference intheir entirety.

BACKGROUND OF THE INVENTION

The present invention generally relates to surgical instruments andmethods for use of the same, and more particularly, but not exclusively,relates to instruments and methods for stabilizing bony structures.

The use of various devices and methods for stabilizing bone structureshave been used for many years. For example, the fracture of an elongatedbone, such as a femur or humerus, can be stabilized by securing a plateto the fractured bone across the fracture. The plate extends across thefractured area and thus stabilizes the fractured components of the bonesrelative to one another in a desired position. When the fracture heals,the plate can be removed or left in place, depending on the type ofplate that is used.

Another type of stabilization technique uses one or more elongated rodsextending between components of a bony structure and secured to the bonystructure to stabilize the components relative to one another. Thecomponents of the bony structure are exposed and one or more boneengaging fasteners are placed into each component. The elongated rod isthen secured to the bone engaging fasteners in order to stabilize thecomponents of the bony structure.

One problem associated with the above described stabilization structuresis that the skin and tissue surrounding the surgical site must be cut,removed, and/or repositioned in order for the surgeon to access thelocation where the stabilization device is to be installed. Thisrepositioning of tissue causes trauma, damage, and scarring to thetissue. There are also risks that the tissue will become infected andthat a long recovery time will be required after surgery for the tissueto heal.

Minimally invasive surgical techniques are particularly desirable in,for example, spinal and neurosurgical applications because of the needfor access to locations deep within the body and the danger of damage tovital intervening tissues. The development of percutaneous minimallyinvasive spinal procedures has yielded a major improvement in reducingrecovery time and post-operative pain because they require minimal, ifany, muscle dissection and can be performed under local anesthesia.These benefits of minimally invasive techniques have also foundapplication in surgeries for other locations in the body where it isdesirable to minimize tissue disruption.

Examples of instruments and techniques for performing surgeries usingminimally invasive techniques are found in U.S. Pat. Nos. 5,792,044 and5,902,231 to Foley et al. While these techniques are steps in the rightdirection, there remains a need for instruments and methods forstabilizing bony structures using minimally invasive techniques. Thisneed and others are addressed by the present invention.

SUMMARY OF THE INVENTION

The present invention relates to devices and methods for insertion of anorthopedic brace to one or more anchors secured to an animal subject.

In one aspect of the invention, there is provided a method for using aninstrument to connect at least two bone anchors with a connectingelement. The instrument is secured to the anchors and manipulated toplace the connecting element in a position more proximate the anchors.

In another aspect of the present invention, there is provided a methodthat includes: placing at least two anchors in a bony structure, each ofthe anchors having an extension associated therewith; attaching a braceinserter of an installation instrument to the extensions; and guiding abrace into a desired position relative to the anchors.

In a further aspect of the invention, there is provided an instrumentfor placing a brace or connecting element into a desired positionrelative to at least two anchors. The instrument employs a fixedgeometric relationship to guide the connecting element into a positionproximate the anchors.

In yet a further aspect of the invention, there is provided aninstrument for placing a connecting element into a desired positionproximate the location of two anchors. The instrument is mounted to theat least two anchors and holds the connecting element in spatialrelation to the anchors about a pivot point. The instrument is rotatedabout the pivot point to guide the connecting element to the desiredposition.

According to an additional aspect of the invention, there is provided aninstallation instrument having a brace secured thereto. The brace isindexed so that the brace can assume only a desired orientation whensecured to the installation instrument.

According to one aspect of the invention, the percutaneous braceplacement device includes first and second anchor extensions and apivoting brace inserter mounted to the anchor extensions about a pivotaxis. The pivoting brace inserter includes an arm having a bracemounting portion at its distal end for connecting an orthopedic brace tothe device.

In another aspect of the present invention, the installation instrumentincludes a support arm engaged to the anchor extension. An anchor isengaged to the distal end of each anchor extension. Preferably, theanchors are in the form of a multi-axial screw capable of allowinguniversal rotation of the anchor extension. In one form, the arm islocated at a predetermined radius from the pivot axis and in a curve ata substantially constant radius relative to the pivot axis to the bracemounting portion. In yet another form, a brace gripper or coupler isoperable to selectively grip and release an orthopedic brace from theinserter. In another form, a brace has one end connected at the bracemounting portion and an opposite end adapted to puncture soft tissue ofan animal body. Preferably, the brace and pivot arm lie in a circlecentered on the pivot axis at a constant radius. The brace is curved atthe constant radius relative to the pivot axis in one plane, and thebrace is oriented to lie in the circle.

According to another aspect of the invention, a method of installing anorthopedic brace in an animal subject is provided. The method comprisesplacing first and second anchors mounted on first and second anchorextensions, respectively, percutaneously in first and second bony partsof the body of the subject; mounting a brace inserter on the anchorextensions, the inserter having a pivot axis about the anchorextensions; mounting the brace on the pivoting brace inserter; andswinging the brace inserter elative to the anchor extensions about thepivot axis and thereby moving the brace in a forward direction throughan arc centered on the pivot axis and introducing an end of the bracepercutaneously to the location of the anchors. In a further form, thebrace is fixed to the anchors; the inserter disconnected from the brace;and the inserter moved in a reverse direction through the arc and toremove the inserter from the body. Preferably, the brace is a shaftcurved at a single radius about an axis co-linear with the pivot axis ofthe arc, and the method further includes introducing the shaft throughreceivers in the anchors during the introduction step.

In yet another aspect of the present invention, anchors, or anchors andanchor extensions are placed by image guided navigation to locateoptimum placement and orientation of the anchors in pedicles ofvertebral bodies of a single level of the spine of the animal. The imageguided technology is also used to determine animal skin locations forpercutaneous puncture entry of the anchors. In one form the anchors arecannulated and inserted over guidewires anchored in the vertebralbodies.

According to another aspect of the invention, a technique for spinalfusion of adjacent vertebral bodies of the animal spine is provided. Themethod includes removal of intervertebral disc material from the spacebetween first and second vertebral bodies of the subject. One or moreinterbody fusion devices are introduced into the space. First and secondanchors are engaged to the first and second vertebral bodies,respectively, through first and second percutaneous punctures in thesubject. A curved brace is installed through a third percutaneouspuncture in the subject using an installation instrument. The brace isconnected to the anchors by application of fastening tool to the anchorsthrough the first and second punctures.

In another form of the present invention, a curved brace is installed byswinging the brace through an arc in a plane containing the brace andperpendicular to the axis of curvature of the brace, and passingportions of the brace into passageways in the anchors. The pivot axis ofthe brace is at a fixed distance from the passageways equal to theradius of curvature of the brace.

One object of the present invention of the present invention is toprovide minimally invasive techniques and instruments for stabilizing abony structure in an animal subject.

Related features, aspects, embodiments, objects and advantages of thepresent invention will be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a brace and an installation instrumentfor installing the brace according to one embodiment of the presentinvention.

FIG. 2 is an enlarged fragmentary section view taken at line 2-2 of FIG.1 and viewed in the direction of the arrows.

FIG. 2a is a side elevational view of another embodiment of a braceinserter.

FIG. 3 is an enlarged fragmentary exploded view of the connection of thebrace to a portion of the installation instrument.

FIG. 3a is an enlarged fragmentary exploded view of another embodimentconnection of the brace to a portion of the installation instrument.

FIG. 4 is an enlarged section view of a portion of the installationinstrument taken at line 4-4 of FIG. 1.

FIG. 5 is an end view, on a smaller scale than FIG. 4, of an outersleeve comprising a portion of the installation instrument of FIG. 1.

FIG. 6 is an enlarged section view of a portion of the installationinstrument taken through line 6-6 of FIG. 1.

FIG. 7 is a perspective view on a much smaller scale than FIGS. 4 and 6of an inner sleeve comprising a portion of the installation instrumentof FIG. 1.

FIG. 8 is a perspective view of a further embodiment of a brave and aninstallation instrument according to the present invention.

FIG. 9 is an exploded perspective view of a portion of the installationinstrument of FIG. 8.

FIG. 9a is a section view taken through line 9 a-9 a of FIG. 9.

FIG. 10 is a side elevational view of the portion of the installationinstrument of FIG.

FIG. 11 is a side elevational view of the brace coupler of theinstallation instrument of FIG. 8.

FIG. 11a is an enlarged detail view of a portion of the brace gripper ofFIG. 10.

FIG. 12 is an enlarged detail view of the portion of installationinstrument connected to an indexed brace.

FIG. 13 is an enlarged view of a trocar and the portion of theinstallation instrument connected thereto.

FIG. 14 is an elevational view eve forming a portion of the anchorextension of the installation instrument of FIG. 8.

FIG. 15 is a right hand end view of the inner sleeve of FIG. 14.

FIG. 16 is a side elevational view of a first outer sleeve forming aportion of the anchor extension of the installation instrument of FIG.8.

FIG. 17 is a side elevational view of a second outer sleeve forming aportion of the anchor extension of the installation instrument of FIG. 8rotated 90 degrees about its longitudinal axis as compared with thefirst outer sleeve of FIG. 16.

FIG. 18 is a perspective view of a guidewire.

FIG. 19 is a perspective view of a cannulated awl usable in a surgicaltechnique with the installation instrument of the present invention.

FIGS. 20a and 20b are perspective views of driver tools usable in asurgical technique with the installation instrument of the presentinvention.

FIG. 21 is a side elevational view of a portion of the spinal column andthe installation instrument along with a cannula for performing surgicalprocedures in the disc space.

FIG. 22 is a top plan view of the instruments of FIG. 21 at the skinlevel.

FIGS. 23 and 24 are perspective views of another embodiment of aninstallation instrument of the present invention usable in a two levelstabilization procedure.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any such alterations and furthermodifications in the illustrated devices, and such further applicationsof the principles of the invention as illustrated herein arecontemplated as would normally occur to one skilled in the art to whichthe invention relates.

The present invention is directed to instruments and methods forinsertion of a brace for connection with anchors engaged to bony partsof the body. Referring to FIG.1, connecting element or brace 90 ispreferably an elongated rod or shaft curved along its length between aconnecting end 91 and an insertion end 92 with a radius of curvature R.However, it should be understood that the present invention contemplatesthat brace 90 can include any configuration known for a rod, implant, orfastener, so long as brace 90 is insertable using installationinstrument 20. Further, brace 90 can be elastic or super-elastic memberin the form of a cable, band or artificial ligament that used intethering or other surgical procedures. Brace 90 can be percutaneouslyor non-percutaneously inserted with an installation instrument 20 intopassageways of anchors engaged to a bony structure in the body of ananimal subject to stabilize the bony structure.

In the illustrated embodiment, brace 90 is a shaft curved at a singleradius R along an arc A, and brace 90 has an axis co-linear with arc A.However, it is contemplated that brace 90 can have a curvature thatdiffers from arc A, or can have a curvature that varies or is compoundedalong its length. The curvature of brace 90 can be defined by any one orany combination of mathematical relationships, including, for example,linear, exponential, logarithmic, trigonometric, geometric, parabolic,quadratic, cubic, hyperbolic, elliptic, or parametric relationships.Brace 90 in FIG. 1 is inserted via the installation instruments of thepresent invention through passageways 70 a and 70 b of anchors 60 a and60 b, respectively in order to stabilize adjacent vertebrae V1 and V2.The installation instrument can employ any type of fixed geometricrelationship to insert brace 90 into passageways 70 a and 70 b. Thisfixed geometric relationship can be governed any one or combination of apinned joint, a cam, a four-bar linkage, a guide member that provides apath for translational movement of brace 90, or any other mechanicalrelationship that would occur to those skilled in the art.

Installation instrument 20 illustrated in FIG. 1 includes a firstsupport arm 22 a and a second support arm 22 b. Support arms 22 a, 22 bare pivotally connected at a proximal end 32 of a brace inserter 24.Brace inserter 24 includes a distal end 33 from which a brace 90extends. A pivot arm 31 has a straight portion 31 a extending fromproximal end 32 to a curved portion 31 b that extends to a bracemounting portion 25 at distal end 33. Inserter 24 is pivotable about apivot axis P to define a curvilinear arc or axis A. Brace mountingportion 25 includes a brace receiving opening 35 at distal end 33.

Preferably, brace 90 is supported by mounting portion 25 in receivingopening 35 so that brace 90 is relatively fixed with respect to inserter24, maintaining alignment of brace 90 along arc axis A during insertionof brace 90. Curved portion 31 b includes a channel 34 extendingtherealong that receives a brace coupler 36 therein. Preferably, bracecoupler 36 is an elongated pin that extends along arc axis A from distalend 33 to a thumb screw 37 adjacent pivot arm 31. As shown in FIG. 3,brace coupler includes an elongated pin having a distal end 36 a that ispreferably threaded, and is received within an internally threaded bore93 formed at brace connecting end 91. It is further contemplated thatthe pin can be a wire or a flexible rod. Thumb screw 37 is manipulatedby the surgeon to connect brace 90 to inserter 24 at brace mountingportion 25. After brace 90 is inserted, the surgeon manipulatesthumbscrew 37 to disconnect brace 90 from inserter 24.

The present invention also contemplates other mechanisms for connectingbrace 90 to inserter 24. For example, in FIG. 3a brace coupler 36includes a draw bar 140 positionable within channel 34. Bar 140 has adistal end 142 with a pair of opposed jaws 143 forming a mouth 145. Eachjaw 143 includes a tooth 144 projecting therefrom towards the opposingjaw. Brace 90′ is the same as brace 90, except brace 90′ has aconnecting end 91′ with a connecting post 94 extending therefrom.

Connecting post 94 is tapered from connecting end 91′ to tip 96, and isconfigured to mate with jaws 143 in mouth 145 when jaws 143 are clampedaround connecting post 94. Connecting post 94 includes a recess 95formed adjacent connecting end 91′ configured to receive teeth 144therein. In order to clamp connecting post 94, a proximal end of drawbar 140 extends from inserter 24, as shown in FIG. 1 with respect tocoupler 36, and has a threaded thumbscrew engaged thereto. The jaws areactuated and clamped around connecting post 94 by threading thethumbscrew in an appropriate direction to draw bar 140 into channel 34.Jaws 143 are pressed towards one another and teeth 144 are received intorecess 95, thereby connecting brace 90′ to inserter 24. Preferably,connecting post 94 is indexed so that brace 90′ can only be coupled toinserter 24 with brace 90′ extending along axis A. This indexing can beaccomplished by providing two recesses 95 each sized to receive tooth144 and positioned on post 94 such that brace 90′ can only be coupledvia teeth 144 if brace 90′ is oriented along axis A.

Inserter 24 has a bottom surface 25 a that is preferably curved alongaxis A to facilitate smooth percutaneous insertion of brace 90. Further,curved portion 31 b has at mounting portion 25 a thickness t1betweenbottom surface 25 a and a top surface 25 b. The thickness increasesalong the length of curved portion 31 b of pivot arm 31 in a smoothtaper to a thickness t2 adjacent the straight portion 31 a. Thickness t2is preferably greater than thickness t1, facilitating percutaneousinsertion and withdrawal of curved portion 31 b while minimizing damageand trauma to the surrounding tissue.

Support arms 22 a and 22 b have proximal end portions adjacent axis Pwith tool bores 26 a and 26 b, respectively, for receiving a drivingtool therethrough to manipulate anchors 60 a and 60 b, respectively, asdescribed further below. In the illustrated embodiment, support arm 22 aincludes an upper post 28 a having a channel 23 a extending upwardly tothe proximal end portion and communicating with tool bore 26 a. Ananchor extension 30 a is mounted in channel 23 a via a thumbscrew 27 athreadedly received in a threaded aperture 29 a that extends throughupper post 28 a and anchor extension 30 a. Anchor extension 30 a ismounted at its lower or distal end to anchor 60 a. Similarly, supportarm 22 b includes an upper post 28 b having a channel 23 b communicatingwith tool bore 26 b. An anchor extension 30 b is mounted in channel 29 bvia a thumbscrew 27 b threadedly received in a threaded aperture (notshown) extending through upper post 28 b and anchor extension 30 b.Anchor 30 b is mounted at its lower or distal end to anchor 60 b. Thepresent invention also contemplates that upper post 28 a and anchorextension 30 a, and similarly upper post 28 b and anchor extension 30 b,are not separate components but rather are formed as a unit to whichbrace inserter 24 is pivotably attached.

Inserter 24 is pivotally connected to upper posts 28 a and 28 h ofsupport arms 22 a and 22 b, respectively. As shown in FIG. 2, across-section taken at line 2-2, inserter 24 is positioned betweensupport arms 22 a and 22 h. Upper post 28 a has a cylindrical portion 46a with a first flanged bushing 47 a extending therefrom. Upper post 28 bhas a cylindrical portion 46 h with a second flanged bushing 47 bextending therefrom. Bushings 47 a and 47 h are rotatably received in athrough-hole 39 that extends through pivot arm 31. Bushings 47 a and 47h define a through opening 48 for receiving a pin 49 therein to secureposts 28 a and 28 h to pivot arm 31. Preferably, pin 49 is threadedalong a portion of its length to engage internal threads in bushing 47a, and the head of pin 49 sits within a countersink formed incylindrical portion 46 b at bushing 47 b to maintain clearance of bore26 b.

An alternate form of pivot arm 31 for pivoting rod inserter 24 isillustrated in FIG. 2a and designated as rod inserter 24′, and likeelements between inserter 24 and 24′ are designated with like referencenumerals. Inserter 24′ has pivot arm 122 extending from curved portion31 b to a proximal end 123. A handle 128 is positioned adjacent bracemounting portion 25 on pivot arm 122 to facilitate percutaneousinsertion of brace 90 and withdrawal of the instrument by the surgeon. Apair of arms 124, 126 adjacent proximal end 123 form a passagetherebetween. The passage is configured to receive support arms 22 a, 22b between arms 124 and 126. Holes 125 and 127 formed through arm 124 and126, respectively, are provided for a connection mechanism to pivotallyconnect inserter 24′ to support arms 22 a and 22 b.

Referring now to FIG. 4, details of anchor extensions 30 a and 30 b andanchors 60 a and 60 b (hereinafter collectively referred to as anchorextension 30 and anchor 60) will now be described. In FIG. 4, anchor 60is shown fragmentarily as a bone screw 61 with its head 63 mounted in areceiver or connector. In FIG. 1, screws 61 a and 61 b are showncannulated with central passage 85 a and 85 b, respectively; however,non-cannulated screws 61 are also contemplated.

In the illustrated embodiment, the receiver or connector is a yoke 68that defines a passageway 70 for receiving brace 90 therethrough and aset screw 76 to secure brace 90 in yoke 68. Yoke 68 is mountable toanchor extension 30 before and during percutaneous placement andsecurement of anchor 60 to the bony structure. Anchor extension 30includes an outer sleeve 40 and an inner sleeve 50 disposed within abore 45 through outer sleeve 40. Inner sleeve 50 defines a bore 51therethrough that communicates with the channel and tool bore 26 of theupper post 28 to which inner sleeve 50 is attached (FIG. 1). Distal end53 of inner sleeve 50 includes a lip 52 extending radially therearoundprojecting into inner bore 51. Lip 52 retains set screw 76 on innersleeve 50 with screw 76 at least partially threaded into yoke 68,thereby mounting anchor 60 on anchor extension 30.

Screw 61 has bone engaging threads formed on shank 62 and a head 63 thatincludes tool opening 64, such as a hex opening or the like, configuredto receive a driving tool. In a preferred form, anchor 60 is amulti-axial screw assembly that has yoke 68 pivotably coupled to head 63of screw 61. However, the use of an anchor 60 that does not include ascrew having multi-axial capabilities is not precluded by the presentinvention. As is known in the art, screw 61 is capable of being rotatedwithin yoke 68 to assume a plurality of angles between axes L1 and L2.Further, screw 61 can be rotated 360 degrees about axis L at any one ofthe angular positions between axis L1 and L2. One specific example of amulti-axial screw having application with the present invention isdescribed in U.S. Pat. Nos. 5,797,911 and 5,879,350, each of which isincorporated herein by reference.

In the illustrated example, anchor 60 includes a connector in the formof a generally cylindrical yoke 68 having passageway 70 therethrough forreceiving brace 90. Head 63 of screw 61 is received within a bowl 69formed at the bottom of yoke 68. A groove 67 is formed in bowl 69, and acollar 65 is retained in bowl 69 via groove 67. Collar 65 captures screw61 in yoke 68, and is configured to mate with head 63 to allowmulti-axial orientations of screw 61 as described above. A cap 66 ispositioned over head 63 and limits upward displacement of screw 61 inyoke 68.

Yoke 68 includes arms 71 extending upwardly from bowl 69 on oppositesides of passageway 70. Arms 71 have internal threads 72 configured tomate with external threads 77 on set screw 76. Set screw 76 has uppertool engaging portion 78 having tool dimension d2 and a lower toolengaging portion 79 having tool dimension d1 that is less than d2. Setscrew 76 has a shoulder 80 that is supported on inner sleeve 50 by lip52. Set screw 76 is positioned with shoulder 80 on lip 52 by threadingexternal threads 77 past lip 52. In FIG. 4, set screw 76 is partiallythreaded into internal threads 72 of yoke 68 in order to couple anchor60 to anchor extension 30. Upper tool engaging portion 78 has a reducedthickness portion 81 where it joins lower tool engaging portion 79.Thus, in this embodiment, set screw 76 is a break-off type set screwwhich severs at reduced thickness portion 81 when a predeterminedthreshold torque is applied at upper tool engaging portion 78, thusallowing a desirable and uniform securing force to be applied to brace90 with each of the set screws 76. Another advantage is that set screw76 can be released from anchor extension 30 when set screw 76 issevered.

Yoke 68 is received within recess portion 42 at distal end 41 of outersleeve 40. As shown in FIG. 5, an end view of outer sleeve 40, recess 42is shaped with a generally cylindrical wall with a couple of flatsurface to conform to the outer perimeter of yoke 68 at upper endsurfaces 73. Upper surfaces 73 of arms 71 are held firmly againstrecessed surface 44 by set screw 76, which is releasably coupled to yoke68 and inner sleeve 50, by drawing yoke 68 into recess 42 via innersleeve 50. Anchor 60 is mounted to anchor extension 30 and held in afixed position relative to anchor extension 30. Axis L3 of anchorextension 30 is aligned with axis L1 of bone screw 61 when a guidewire,such as guidewire 280 of FIG. 18, or a tool, such as tool 100 or 100′ ofFIGS. 20 and 20 b is inserted into screw 61 to maintain anchor 60 inthis aligned position.

Referring to FIGS. 6 and 7, inner sleeve 50 and its connection withouter sleeve 40 will be further described. Inner sleeve 50 includeslower cylindrical tubular body portion 53. Fingers 54 extend from bodyportion 53 to upper end 55 of inner sleeve 50. Fingers 54 includeretainers 56 adjacent upper end 55. A pin or nub 58 is positioned on andextends from the outer surface of each finger 54. Outer sleeve 40includes upper paired holes 57 a and lower paired holes 57 b, whichserve as catches. As shown in FIG. 6, nubs 58 are positionable withincatches 57 a or 57 b formed in outer sleeve 40 to hold inner sleeve 50relative to outer sleeve 40. Retainers 56 contact upper end 46 of outersleeve 40 when nubs 58 are positioned in lower catches 57 b. Retainers56 limit the depth of insertion of inner sleeve 50 into bore 45 of outersleeve 40. Retainers 56 also facilitate insertion and withdrawal ofinner sleeve 50 relative to outer sleeve 40 by providing the surgeonmeans to grasp fingers 54 and squeeze.

Finger 54 can be deflected towards one another as indicated by arrows Pin order to disengage nubs 58 from catches 57 a and 57 b, thus allowingrotation and axial translation of inner sleeve 50 in outer sleeve 40.Outer sleeve 40 includes notches 59 formed at upper end 46 on oppositesides of outer sleeve 40 between respective ones of the paired catches57 a and paired catches 57 b. Notches 59 allow inner sleeve 50 to bepositioned in outer sleeve 40 with nubs 58 at a depth approximating thelocation of catches 57 a and 57 b without deflecting fingers 54. Fingers54 can then be pressed together to withdrawal nubs 58 from notches 59,allowing inner sleeve 50 to be rotated and nubs 58 positioned in thedesired paired catches 57 a or paired catches 57 b.

With nubs 58 positioned in lower catches 57 b, set screw 76 extends intorecess portion 42 of outer sleeve 40 enough to allow anchor 60 to bemounted on extension 30 by threading set screw 76 partially into yoke68. Nubs 58 can then be positioned in upper catches 57 a, retractingyoke 68 into recessed portion 42 of outer sleeve 40 to hold anchor 60firmly in place as shown in FIG. 4 and described above. Anchor 60 canthus be pre-assembled with anchor extension 30 before engaging anchors60 to the bony structure, allowing the assembled anchor 60 and anchorextension 30 to be positioned percutaneously together in a minimallyinvasive approach to the bony structure. However, it is alsocontemplated that anchor extension 30 can be mounted on an anchor 60that is already engaged to the bony structure.

Referring now to FIGS. 8 and 9, another embodiment of an installationinstrument is illustrated. In FIG. 9, anchor extensions 230 are notillustrated. Anchor extensions 230 include an inner sleeve 240 that isreceived proximally within outer sleeve 250 in a manner similar to thatdescribed above with respect to anchor extension 30. The inner sleeve240 and outer sleeve 250 are further illustrated in FIGS. 14-17, and aredescribed in further detail below.

Installation instrument 220 includes a brace inserter 224 having a firstsupport arm 222 a and a second support arm 222 b. Support arms 222 a,222 b come together and are fixedly connected at a proximal end 232 of apivot arm 231. Referring now further to FIGS. 9a and 10, pivot arm 231includes a distal end 233 from which brace 290 extends. Brace inserter224 includes a brace mounting portion 225 adjacent distal end 233 forsecuring a brace, such as brace 290, thereto. Brace 290 is similar tobrace 90, and includes a connecting portion 291 as described furtherbelow. Brace inserter 224 is pivotable about a pivot axis P to define acurvilinear arc or axis A. Pivot arm 231 of brace inserter 224 ispreferably curved along curved portion 231 b to follow axis A andfacilitate smooth percutaneous insertion and withdrawal of pivot arm231. As shown in FIG. 9a , brace mounting portion 225 includes a bracereceiving opening 235 extending proximally from distal end 233.

Pivot arm 231 includes a channel 234 extending from distal end 233therealong towards proximal end 232. Channel 234 receives a bracecoupler 236 therein that is secured to inserter 224 by a nut 239 and pin228. For the purposes of clarity, nut 239 and brace coupler 236 areshown displaced from channel 234 except at distal end 233. Preferably,brace coupler 236 is an elongated flexible member that extends with arcaxis A from distal end 233 through nut 239 to a set screw 237 adjacentproximal end 232. Coupler 236 is pivotably coupled to inserter 224 atbrace mounting portion 225 via pin 228. Set screw 237 is threadinglyreceived in a threaded opening formed in nut 239. Brace mounting portion225 also includes stop pin 229 extending therethough in communicationwith brace receiving opening 235.

Referring now further to FIGS. 11-12, brace 290 is positionable in bracereceiving opening 235 so that brace 290 is relatively fixed with respectto inserter 224 by brace coupler 236, maintaining alignment of brace 290along arc axis A during insertion of brace 290. Brace coupler 236includes gripping portion 270 at its distal end for gripping brace 290.Gripping portion 270 has through-hole 272 receiving pin 228 therethroughand rotatably coupling gripping portion 270 at brace mounting portion225. Gripping portion 270 further includes a tooth 274 extendingtherefrom at its distal end 271. A notch 276 extends proximally fromtooth 274.

Brace 290 has a connecting end 291 with a connecting post 294 extendingtherefrom. Preferably, connecting post 294 is tapered from connectingend 291 to tip 296, and has a recess 297 with a length and depthconfigured to receive tooth 274 at the end of the recess 297 adjacenttip 296 and stop pin 229 at the end of recess 297 adjacent connectingend 291. Stop pin 229 contacts brace 290 in recess 297 to limit thedepth of insertion of brace 290 into opening 235.

In one aspect of the invention, brace 290 is indexed by providing asingle recess 297 at a predetermined location on post 294. Post 294cannot be inserted properly into channel 235 unless stop pin 229 isreceived in recess 297, thus ensuring an orientation of brace 290 withrespect to inserter 224 that is determined by the position of recess 297with respect to stop pin 229. Preferably, the position of recess 297 issuch that it is located with respect to gripping portion 270 so that theradius of curvature of brace 290 extends from inserter 224 along arcaxis A. This ensures accurate positioning and orientation of brace 290with respect to anchors 60 during installation of brace 290.

In order to grip brace 290 when connecting portion 291 is placed intoopening 235, gripping portion 270 is rotated downwardly about pin 228 inthe direction of arrow R by drawing brace coupler 236 proximally viathreading of set screw 237 in a first direction with respect to lock nut239. Set screw 237 is threaded in an opposite second direction to pushbrace coupler 236 distally and therefore bend coupler 236, rotatingtooth 274 about pin 228 in the direction opposite arrow R out of recess297 thereby releasing brace 290.

Referring back to FIGS. 8 and 9, support arms 222 a and 222 b havethrough-holes 223 a, 223 b for receiving a clamping mechanism 221.Clamping mechanism 221 draws arms 222 a, 222 b towards one another topivotably secure anchor extensions 230 a, 230 b therebetween. Pivot nuts225 a and 225 b are positionable in through holes 223 a and 223 b,respectively. A clamping bar 225 extends between arms 222 a and 222 b,and has threaded bores at each end that allow bar 225 to be secured toand clamp arms 222 a, 222 b via threaded fastener 226 and clamping knob227 having a threaded stem 227 a. Clamping knob 227 is manipulated bythe surgeon to secure or release extensions 230 a and 230 b from arms222 a and 222 b.

In the illustrated embodiment, pin 260 a is press fit into opening 262 aof arm 222 a. Anchor extension 230 a is rotatably mounted on support arm222 a via pin 260 a. Similarly, anchor extension 230 b is rotatablymounted on support arm 222 b via pin 260 b press it into opening 262 bof arm 222 b. Other techniques for securing pins 260 a, 260 b andmounting extensions 30 a, 30 b thereto are also contemplated as wouldoccur to those skilled in the art. Each arm 222 a, 222 b can be providedwith a stop bar 264 a, 264 b extending therefrom towards the othersupport arm 222 b, 222 a, respectively. Stop bars 264 a and 264 b limitrotation of instrument 220 along axis A when stop bars 264 a, 264 bcontact a corresponding one of the extensions 230 a, 230 h.

Referring now to FIGS. 14-17, anchor extensions 230 that coupled toinserter 224 will now be described in further detail. These anchorextensions 230 are illustrated in an assembled condition in FIG. 8. Itshould be noted that second outer sleeve 240 b of FIG. 17 is illustratedrotated 90 degrees about its longitudinal axis as compared with theorientation of the elevational view of first outer sleeve 240 a of FIG.16.

Although anchors are not shown in FIG. 8, anchor extension 230 a canhave mounted thereon at its lower or distal end a first anchor, such asanchor 60 a described above. Similarly, anchor 230 b can have mounted atits lower or distal end a second anchor, such as anchor 60 b, describedabove. Anchor extensions 230 a, 230 b, collectively referred to asanchor extensions 230, each include outer sleeve 240 and an inner sleeve250 disposed within a bore 245 through outer sleeve 240. Inner sleeve250 defines a bore 251 therethrough that allows tools to extend to theanchor. Distal end 253 of inner sleeve 250 includes a lip 252 extendingradially therearound projecting into inner bore 251. Lip 252 supports aset screw, such as set screw 76 described above, on the distal end ofinner sleeve 250.

Yoke 68 is preferably received within end portion 242 at distal end 241of outer sleeve 240. As shown in FIG. 16, end portion 242 has a U-shapedopening that is alignable with passageway 70 to accommodate insertion ofbrace 290 therethrough. The arms 244 of end portion 242 are alignablewith the arms 71 of yoke 68, receiving arms 71 therein, firmly securinganchor 60 onto anchor extension 230 during insertion of the anchor.

The positioning of inner sleeve 250 into outer sleeve 240 will befurther described, although those skilled in the art will appreciatethat anchorextension 30 and anchor extension 230 are similar in manyrespects. Inner sleeve 250 includes lower gripping elements or fingers254 that include circular relief portions 277 therebetween to allowflexing of fingers 254. Inner sleeve 250 further includes upper notch256 and lower notch 256′ between fingers 254 and upper end 255. Outersleeve 240 includes a plunger-type spring biased retainer 257 extendingtherein adjacent bore 245 having a cross bar 258 extending transverselyfrom a plunger 259. Cross bar 258 is selectively positionable in adesired one of the notches 256 and 256′ to hold inner sleeve 250relative to outer sleeve 240. Shoulder 261 limits the depth of travel ofinner sleeve 250 distally into bore 245 of outer sleeve 240. When crossbar 258 is in upper notch 256, set screw 76 of anchor 60 can be threadedonto or pushed between fingers 254 at distal end 253, where set screw 76is retained thereon by lip 252.

If not already secured to set screw 76, yoke 68 can then be at leastpartially threaded onto set screw 76. Movement of inner sleeve 250relative to outer sleeve 240 is facilitated by depressing plunger 259 tolift cross bar 258 out of upper notch 256. Inner sleeve 250 is movedproximally to position cross bar 258 in lower notch 256′, drawing yoke68 between the arms 244 and against end portion 242 with passage 70aligned with the U-shaped opening between the arms 244. Axis L3 ofanchor extension 230 is aligned with axis L1 of bone screw 61 when aguidewire or a tool, such as tool 100 or 100′ of FIGS. 20 and 20 b isinserted into screw 61 to maintain anchor 60 in this aligned position.An alignment pin 263 of inner sleeve 250 is received in slot 249 ofouter sleeve 240 to ensure and maintain proper alignment of inner sleeve250 in outer sleeve 240.

The assembly of anchor extensions 230 a and 230 b to one another andalso to inserter 224 will now be described. Each anchor extension 230includes passage 248 through outer sleeve 240 adjacent the proximal end243. A coupling pin 249 a is press fit or otherwise secured in passage248 a on the side of anchor extension 230 a adjacent anchor extension230 b. After anchor extensions 230 a and 230 b and anchors 60 a and 60 bare secured to bony structure, anchor extensions 230 a and 230 b aremanipulated through the skin and tissue to place pin 249 a into theportion of passage 248 b adjacent anchor extension. 230 a. Inserter 224is secured to anchor extensions 230 a and 230 b by placing pin 260 a ina portion of passage 248 a of first extension 230 a opposite pin 249 a,and pin 260 b in a portion of passage 248 b of second extension 230 bopposite pin 249 a. Pins 260 a and 260 b are rotatably received in thepassages 248 a and 248 b, respectively, and anchors extension 230 a and230 b are secured to support arms 222 a and 222 b via clamping mechanism221. Bores 251 a and 251 b of inner sleeves 250 a and 250 b remainsubstantially unobstructed for access to anchors 60 a and 60 h wheninstrument 220 is assembled.

Techniques using the above described installation instruments 20, 220will now be described. The present invention contemplates that placementof anchors 60 into the bony structure can be completed without an anchorextension 30 or 230 mounted thereto, and anchor extension 30 or 230 isthereafter mounted on the anchor 60 engaged to the bony structure. Othertechniques contemplate that the anchor 60 is mounted on anchor extension30 or 230, and anchor extension 30 or 230 and anchor 60 are placedthrough an open incision, micro-incision, a tube or cannula, or directlythrough the skin and tissue of the animal subject to engage anchor 60 toa bony structure, such as the pedicles of vertebrae V1 and V2 as shownin FIG. 1.

The surgical techniques of the present invention can employ any type ofknown imaging system to determine and locate optimum placement andorientation of the anchors in the bony structure and, if necessary, tolocate skin locations for percutaneous puncture entry of the anchors.Image guided systems useful in practicing the invention and in placinganchors 60 are known in the art. Examples of image guided technology areprovided in U.S. Pat. Nos. 5,772,594; 5,383,454; 5,851,183; 5,871,445;5,891,034; and PCT Publication WO 99/115,097, each of which isincorporated herein by reference in its entirety. The STEALTHSTATION® orION™ systems, sold by Medtronic Surgical Navigation Technologies, Inc.can further be used with the present invention for pre-operativeplanning and image guided navigation of anchor placement andinstallation of brace 90.

Other techniques for locating and placing anchors 60 into the bonystructure are also contemplated herein as would occur to those skilledin the art. For example, a CT scan or x-ray can be used forpre-operative planning of anchor positioning and orientation. Anchorinsertion can be monitored using any known viewing instrument orapparatus. Another example contemplates anchor placement through acannula or sleeve inserted through the skin that forms a working channelto the anchor location. Anchor placement into the bony structure can bemonitored endoscopically or microscopically through the cannula.

In one specific technique, a guidewire, such as guidewire 280 of FIG.18, of sufficient length is inserted percutaneously and anchored to thebony structure. The guidewire is coupled to a trackable instrument thatis tracked via an image guided surgical system that generates a displayon a computer monitor. Further examples of such instruments and systemsare described in further detail in PCT Publications WO 99/15097 and WO99/26549, each of which is incorporated herein by reference in itsentirety. With the guidewire secured at the appropriate location on thebony structure, various instruments for preparing and inserting thescrew into the bony structure can be guided by the guidewire. Thepreparation and insertion can be monitored via a tracking instrumentcoupled to the various preparation and insertion instruments.

Various instruments can be used to prepare the surgical site for anchorinsertion. For example, in FIG. 19 there is illustrated a cannulated awl300 that is inserted over the guidewire to prepare the bony structurefor screw insertion. Awl 300 has a bore 306 extending between distal end303 and proximal end 302 that allows awl 300 to be inserted over theguidewire. Awl 300 is configured at proximal end 302 to engage a drivinginstrument, which can also include a tracking instrument to monitorinsertion depth. Awl 300 has shaft 304 extending to distal end 303. Acutting head 307 at distal end 303 prepares a hole in the bony structurefor the anchor.

After determining the desired position and orientation of guidewire 280in the bony structure and the skin location for puncture entry andpreparing the screw hole, a cannulated anchor 60 mounted on anchorextension 30 or 230 can be placed over the guidewire and advanced, forexample, through the skin and tissue directly, through an incision, orthrough a cannula to the prepared hole. A driving tool, such ascannulated driving tool 100′ shown in FIG. 20a , is used to threadinglyengage anchor 60 to the bony structure. Cannulated tool 100′ includesbore 106′ extending between proximal end 102′ and distal end 103′.Distal end 103′ includes an engaging portion 107′ to mate in toolengagement recess 64 of screw 61. Tool 100′ is placed over the guidewireand through the tool bores of the anchor extensions 30, 230 to drive thecannulated screw 61 into the bony structure.

It is further contemplated that if the technique does not employ aguidewire, a driving tool 100 of FIG. 20b can be inserted through thetool bores of the anchor extensions 30, 230 to screw 61. Tool 100includes proximal end 102 and a shaft 104 extending to distal end 103.Proximal end 102 is preferably configured to engage a wrench or handleto facilitate application of a driving force with tool 100. Distal end103 includes a lower engaging portion 107 having a length configured tomate in tool engagement recess 64 of screw 61 to drive screw 61 into thebony structure.

Anchor extension 30, 230 follows anchor 60 towards the bony structure asanchor 60 is driven therein with driving tool 100 or 100′. Tool 100 isthen withdrawn from the tool bore, and if necessary, the guidewire isalso withdrawn. In embodiments of anchor 60 having a multi-axial screw,yoke 68 and anchor extension 30, 230 are pivotable about head 63 bymanipulating anchor extension 30, 230 in the skin and tissue to thedesired position.

With anchors 60 a and 60 b secured to the bony structure, passageways 70a and 70 b are aligned to receive brace 90. For instrument 20, upperposts 28 a and 28 b are mounted on anchor extensions 30 a and 30 b usingthumb screws 27 a and 27 b, respectively, aligning passageways 70 a and70 b. With anchors 60 employing a multi-axial screw, the anchorextensions 30 a and 30 b can be manipulated into the desired positionfor connection with upper posts 28 a and 28 b. For instrument 220,anchor extensions 230 a and 230 b are manipulated to place pin 249 a inpassage 248 b, aligning passageways 70 a and 70 b. Support arms 222 aand 222 b are secured to anchor extensions 230 a and 230 b with clampingmechanism 220. If anchor 60 does not have multi-axial capabilities, theorientation of the anchor extensions required to connect the inserterthereto is accounted for during the determination of the orientation andpositioning anchors 60 a and 60 b into the bony structure.

Brace 90, 290 is fixed on inserter 24, 224 and readied for percutaneousinsertion into passageways 70 a and 70 b of anchors 60 a and 60 b,respectively. Preferably, brace 90, 290 is curved and has a radius ofcurvature equal to the distance between passageways 70 a, 70 b and pivotaxis P. Inserter 24, 224 swings about pivot axis P to move brace 90 in aforward direction along arc axis A and thereby introducing pointed endof brace 90, 290 into the subject's body towards the aligned passageways70 a and 70 b. Brace 90, 290 and inserter 24, 224 are further pivoted topass portions of brace 90 through passageways 70 a and 70 b of anchors60 a and 60 b.

As discussed above, it is preferred that brace is indexed so that it canbe secured at a predetermined orientation onto the installationinstrument 20, 220. This ensures alignment of brace 90, 290 along theinsertion path of the installation instrument and through thepassageways of anchors 60 a and 60 b. In a further form, trocar 390, asshown in FIG. 13, can be used to puncture skin and tissue along theinsertion path and facilitate insertion of brace 90, 290 in apercutaneous procedure. Trocar 390 has a connecting end 394 identical tothat of brace 290. However, trocar 390 has a short shaft 392 extendingto puncture tip 398. Puncture tip 398 has a sharp point 399 tofacilitate insertion and create a pathway through skin and tissue of thepatient.

Brace 90, 290 is placed through the passageways of anchors 60 a and 60 bto the desired position, which can be confirmed radiographically or withany know imaging technique. Setscrews 76 a and 76 b of each anchor 60 aand 60 b are driven downward to contact brace 90, 290. A driving tool isplaced through the tool bores of the installation instruments 20, 220 toengage either the upper tool engagement portion 78 a, 78 b or lower toolengagement portion 79 a, 79 b and drive set screw 76 a, 76 b downwardly,tightening it against brace 90, 290 until set screw 76 a, 76 b is firmlyseated thereagainst. Inserter 24, 224 can then be uncoupled from brace90, 290 and removed from the subject by swinging inserter 24, 224 backalong arc axis A. A tool is positioned in upper tool engagement portion78 a, 78 b to break off the upper portion of the set screw 76 a. 76 bupon application of the requisite torque, releasing the anchor extension30 a, 30 b from anchor 60 a, 60 b and allowing removal of extensions 30,230 from the subject.

The surgeon may also desire to initially seat set screw 76 a, 76 b usinga tool in upper tool engagement portion 78 a, 78 b and apply sufficienttorque to severe the break-off portion of set screw 76 a 76 b beforeuncoupling brace 90, 290. In an alternate form, the driving force thatis applied to set screw 76 a, 76 b could force shoulder 80 a, 80 bthrough lip 52 a, 52 b, deflecting lip 52 a, 52 b downward to releaseset screw 76 a, 76 b from inner sleeve 50 a, 50 b of instrument 20 ordeflect fingers 154 a, 154 b outward to release set screw 76 a, 76 bfrom inner sleeve 150 a, 150 b of instrument 220.

In one specific application of the present invention, brace 90 isinstalled to stabilize a first vertebra V1 and second vertebra V2 afterplacement of one or more implants I into disc space D as shown in FIG.21. The method includes removing the intervertebral disc from the spacebetween first and second vertebral bodies through one percutaneouspuncture in the subject. An implant I is introduced into the disc space.Implant I is preferably one or more interbody fusion devices or the likeas is known in the art. The first and second anchors 60 a and 60 b andanchor extensions 30 a and 30 b are engaged to the first and secondvertebral bodies, respectively, through second and third percutaneouspunctures in the subject as described above. If desired, the anchorextensions 30 can be manipulated by the surgeon to apply a load tocompress or distract the vertebrae prior to installing brace 90.

Brace 90 is installed through a fourth percutaneous puncture in thesubject using installation instrument 20 and secured to anchors 60 a, 60b as described above. In some surgical procedures, it may be desirableto insert one or more additional braces to stabilize the bony structureusing the above described installation instrument and techniques.

The present invention has application in further minimally invasive andopen techniques for placing interbody fusion device into a disc spacebetween adjacent vertebrae. For example, transforaminal, posterior, andposterior-midline approaches to the disc space are contemplated forplacement of one or more implants or interbody fusion device in the discspace. Such techniques are described in a provisional applicationentitled “Methods and Instruments for Endoscopic Interbody SurgicalTechniques” filed on Oct. 20, 1999 (U.S. Provisional Patent ApplicationSer. No. 60/160,550.) This provisional application is incorporatedherein by reference in its entirety.

As shown in FIG. 21, installation instrument 20 is mounted on anchors 60a and 60 b engaged to vertebrae V1 and V2, respectively. Brace 90 isshown before percutaneous insertion. A cannula 110 is percutaneouslyinserted to a position adjacent disc space D1. As shown in FIG. 22, aplan view taken at skin surface 5, first and second anchor extensions 30a, 30 b and brace 90 are positioned on one side of midline M of thespine. Cannula 110 is positioned on the opposite side of midline M. Oneor more interbody fusion devices, bone graft material, or other materialor implants are placed in the disc space. The adjacent vertebrae VI andV2 are then stabilized by installing brace 90 as described above. Thus,a minimally invasive surgical procedure of the present inventioncontemplates interbody fusion and stabilization of the adjacentvertebrae to be accomplished with four entry holes or punctures throughskin S.

The installation instrument of the present invention can also be used toinstall braces on both sides of midline M of the spine. The installationinstrument can also be used to install multiple braces at one or morelevels of the spine. The present invention can be used to stabilizeadjacent vertebra in conjunction with any minimally invasive or opensurgical techniques for placement of one or more interbody fusiondevices into a disc space as would occur to those skilled in the art.For example, one or more interbody fusion devices or intervertebralspacers may be inserted into the disc space via an anterior approach.Examples of anterior approaches are described in PCT InternationalPublication No. WO 97130666; pending U.S. patent application Ser. Nos.09/287,917; and pending 09/498,426 filed on Feb. 4, 2000; each of whichis incorporated herein by reference in its entirety. Further, thepresent invention may also be used to stabilize adjacent vertebrae, orany other bony structure, without placement of fusion devices orimplants in the bony structure.

It is further contemplated that brace 90 may be installed and secured toanchors engaged in respective ones of three vertebrae using aninstallation instrument such as the one illustrated in FIGS. 23-24 anddesignated generally at 320. Instrument 320 is similar to and functionsprincipally the same as instrument 220, except instrument 320 has a sizeand configuration adapted for this two level stabilization procedure. Inthis embodiment, three anchors that are like anchor 60 (not shown) areengageable to respective ones of three vertebrae or other bony structureusing any of the above described techniques. Three anchor extensions 330a, 330 b, 330 c each include outer sleeves 340 a, 340 b, 340 c and innersleeves 350 a, 350 b, 350 c that are substantially the same as outersleeve 240 and inner sleeve 250 of instrument 220. Anchor extensions 330are each mounted on a corresponding one of the three anchors. Alter theanchors are engaged to the bony structure, the three anchor extensions330 a, 330 b, 330 c are manipulated through the skin and coupled to oneanother in the same manner as described above with respect to anchorextensions 230 a and 230 b. Support arms 322 a, 322 b of inserter 324are then rotatably mounted on the anchor extensions 330 a, 330 b, and330 c and clamped via clamping mechanism 321. Support arms 322 a, 322 band clamping mechanism 321 are similar to support anus 222 a, 222 b andclamping mechanism 221 of installation instrument 220 except that eachis sized to accommodate three anchor extensions 330 therebetween. Anindexed brace 490 is similar to brace 290 and has a sufficient lengthfor a two-level stabilization procedure. Brace 490 is secured to pivotarm 331 and then inserted through the passageways of the anchors asdescribed above with respect to installation instrument 220.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

What is claimed is:
 1. A minimally invasive surgical system comprising:a brace; a first bone anchor having a first head and a first yokedefining a first passageway configured to receive the brace; a firstextension connected with the first bone anchor and configured to extendfrom the first bone anchor through the skin when the first bone anchoris driven in a bony structure such that a portion of the first extensionextending above the skin defines a position of the first passageway, thefirst yoke and the first extension being pivotable about the first head;a second bone anchor having a second yoke defining a second passagewayconfigured to receive the brace; and a second extension connected withthe second bone anchor and configured to extend from the second boneanchor through the skin when the second bone anchor is driven in a bonystructure such that a portion of the second extension extending abovethe skin defines a position of the second passageway, wherein the systemis configured such that when the brace is positioned in the secondpassageway, the portion of the first extension extending above the skinmay be manipulated relative to the portion of the second extensionextending above the skin such that the first passageway is aligned withthe second passageway.
 2. A minimally invasive surgical system asrecited in claim 1, wherein the portion of the first extension extendingabove the skin is configured to be manipulated to move the firstextension relative to the second extension from a first orientation inwhich the first passageway is not aligned with the second passageway toa second orientation in which the first passageway is aligned with thesecond passageway.
 3. A minimally invasive surgical system as recited inclaim 1, wherein the second bone anchor comprises a second head, thesecond yoke and the second extension being pivotable about the secondhead.
 4. A minimally invasive surgical system as recited in claim 1,wherein the second bone anchor does not include multi-axialcapabilities.
 5. A minimally invasive surgical system as recited inclaim 1, wherein the first and second extensions are releasably attachedto the first and second bone anchors.
 6. A minimally invasive surgicalsystem as recited in claim 1, wherein the brace is configured to beside-loaded into the first and second extensions.
 7. A minimallyinvasive surgical system as recited in claim 1, wherein the first andsecond extensions each include a channel, the brace being configured tobe loaded into the channels.
 8. A minimally invasive surgical system asrecited in claim 1, wherein the first and second bone anchors arecannulated so as to fit over guidewires anchored in the bony structures.9. A minimally invasive surgical system as recited in claim 1, whereinthe brace is a spinal rod.
 10. A minimally invasive surgical system asrecited in claim 1, wherein the brace is a spinal rod that is curvedbetween opposite first and second ends thereof.
 11. A minimally invasivesurgical system as recited in claim 1, wherein at least one of the firstand second extensions includes indicia configured to indicate anorientation of the first and second passageways.
 12. A minimallyinvasive surgical system as recited in claim 1, wherein the first andsecond extensions each include indicia configured to indicate anorientation of the first passageway relative to the second passageway.13. A minimally invasive surgical system comprising: a brace; a firstbone anchor having first yoke defining a first passageway configured toreceive the brace; a first extension connected with the first boneanchor and configured to extend from the first bone anchor through theskin when the first bone anchor is driven in a bony structure such thata portion of the first extension extending above the skin defines aposition of the first passageway; a second bone anchor having a secondyoke defining a second passageway configured to receive the brace; and asecond extension connected with the second bone anchor and configured toextend from the second bone anchor through the skin when the second boneanchor is driven in a bony structure such that a portion of the secondextension extending above the skin defines a position of the secondpassageway, wherein the portion of the first extension extending abovethe skin is configured to be manipulated to move the first extensionrelative to the second extension from a first orientation in which thefirst passageway is not aligned with the second passageway to a secondorientation in which the first passageway is aligned with the secondpassageway, and the first bone anchor includes a first head, the firstyoke and the first extension being pivotable about the first head.
 14. Aminimally invasive surgical system as recited in claim 13, wherein thesecond bone anchor comprises a second head, the second yoke and thesecond extension being pivotable about the second head.
 15. A minimallyinvasive surgical system as recited in claim 13, wherein the first boneanchor does not include multi-axial capabilities.
 16. A minimallyinvasive surgical system as recited in claim 13, wherein the second boneanchor does not include multi-axial capabilities.
 17. A minimallyinvasive surgical system as recited in claim 13, wherein the first andsecond bone anchors do not include multi-axial capabilities.
 18. Aminimally invasive surgical system as recited in claim 13, wherein thefirst and second extensions each include a channel, the brace beingconfigured to be side-loaded into the channels.
 19. A minimally invasivesurgical method comprising: driving a first bone anchor including afirst head, and having a first yoke pivotable about the first head intoa bony structure; pivotably connecting a first extension with the firsthead of the first bone anchor such that the first extension extends fromthe first bone anchor through the skin; driving a second bone anchorinto a bony structure; and connecting a second extension with the secondbone anchor such that the second extension extends from the second boneanchor through the skin; positioning a brace within the secondextension; and manipulating the first extension relative to the secondextension to move the first bone anchor from a first orientation inwhich a first passageway of the first bone anchor is not aligned with asecond passageway of the second bone anchor to a second orientation inwhich the first passageway is aligned with the second passageway.
 20. Aminimally invasive surgical method as recited in claim 19, wherein thesecond bone anchor comprises a second head and a second yoke, and thesecond yoke and the second extension pivotably connect about the secondhead.